1. Field of the Invention
The present invention relates to a device and method for detecting explosives. More particularly, the present invention relates to an apparatus and method for generating and detecting Terahertz radiation to positively identify explosive devices carried on human or animal subjects.
2. Description of Related Art
Recent advancements in generation and detection techniques have opened up new opportunities in explosive imaging. More specifically, significant advancements have been made in the use of Terahertz radiation. With current advances, low-power, Terahertz frequencies can be efficiently generated to irradiate a human subject positioned at a short distance from the source.
It is known that organic molecules have unique vibrational and rotational frequencies and that the rotational frequencies lie in the Terahertz regime. The Terahertz waves also have the capability to excite these rotational frequencies within the molecules of explosive materials. The commonly used explosive RDX, for example, has spectral lines at 0.82, 1.05, 1.50, 1.96, 2.20, 3.08 and 6.73 THz. A simultaneous detection of these rotational frequencies or wavelengths through several layers of clothing will constitute a very robust detection of RDX. Other explosives can be similarly detected. In addition to spectral specificity, good imaging resolution is inherently possible as the wavelengths associated with Terahertz waves are short. However, privacy concerns still exist in this kind of imaging.
The role Terahertz frequencies can play in the detection of explosives has been known for some time. However, it has been difficult to make robust THz sources or detectors. Terahertz frequencies (0.5 to 5.0 THz) occupy the region of electromagnetic spectrum that is sandwiched between microwaves and infrared. These frequencies are too high to be produced by conventional electronics and too low to be produced by solid state lasers. Accordingly, the conventional sources of THz are ultra-fast laser switches, pumped gas lasers, optical difference generation techniques, frequency doubling diodes and quantum cascade lasers. All of these require cumbersome equipment and large power sources.
Other detection systems like the Ion Mobility Spectrometer require a small sample of the explosive to be physically brought to the machine for analysis. In the end, none of the prior art discloses an effective and efficient way to detect explosives. Therefore, a need exists to develop a novel alternative that can detect and positively identify explosives in real time without the drawbacks evident in the prior art.